2.2.2 Data Message
The Data Message is exchanged between client and server to send segments of data. The PPP Over IrDA Dialup Protocol relies on the Infrared Network (IrNET) Protocol [MSDN-IRNET] for the pass-through of data messages between the PPP over HDLC-like framing [RFC1662] and TinyTP [IRTTP], for the client and the server.
As specified in [IRTTP] section 2.2.1, the maximum size of a single Data-Carrying TinyTP PDUs packet for a given connection is negotiated by the IrDA Link Access Protocol, as specified in [IRLAP].
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Data Message (variable) |
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Delta Credit (6 bits): The Delta Credit field MUST specify the number (0-63) of additional Data-Carrying TinyTP PDUs that can be sent in the reverse direction, as specified in [IRTTP] section 2.3.1.
M (1 bit): The M field MUST be set to zero, as specified in [IRTTP] section 2.3.1, if this is a single TinyTP PDU. The M field MUST be set to 1 if it is part of, but not the last part of a multi-part TinyTP PDU. That is, if the M bit is set to 1, there are more parts of this PDU to follow.
Data Message (variable): The Data field MUST be ASCII-encoded. The IrDial message MUST NOT exceed the maximum size of a TinyTP PDU, which is negotiated by the IrDA Link Access Protocol, as specified in [IRLAP]. For further details, see [IRTTP] section 2.2.1.
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If the length of the Data field exceeds the maximum size of a single Data-Carrying TinyTP PDU packet, the TinyTP Protocol performs segmentation and reassembly (SAR) of the Data field.